1. Field of the Invention
The present invention relates to television systems, and more specifically to a method and apparatus for accessing data representing various display entities stored in a memory unit of a television system.
2. Related Art
Since the 1940s, television systems have been increasingly embraced by many households, particularly in the industrial countries. Television systems have generally been used to view broadcasts made in distant parts of the world or to view a pre-recorded program from a video cassette player (VCP). A significant proportion of the households presently have at least one television set in their homes. Television displays are presently available or anticipated to be widely available in analog (e.g., NTSC analog signal displayed on a CRT based display screen) as well as digital technologies (e.g., HDTV).
In parallel, data network applications (hereafter "network applications") have experienced a phenomenal growth since the mid--1980s. Network applications such as web-browsing and electronic mail have had a fundamental impact on the manner in which information is exchanged and disseminated. These network applications have particularly been implemented for and used along with computer systems such as personal computer systems, work-stations, and the like.
At least in view of the considerable presence of the television systems in the households, it may be desirable to provide the capability to access network applications on television systems. To provide access to the network applications (or services), images representing network application data may be displayed on a display unit of a television system. Display of network application data is typically achieved by refreshing a display screen with image of the network application data several times in a second.
The data representing network applications (network application data) or pixel data elements representing network application data may be stored in a memory of a television system to facilitate such refresh operations. For each refresh operation, the memory is accessed several times, with data corresponding to a portion of the image being retrieved each time. Accordingly, it may be appreciated that the memory is accessed several times for a typical screen refresh operation.
The memory may be accessed for several other purposes as well. For example, the memory may be accessed to modify the network application data as new data arrives. The memory may be used to store other data as well, requiring even more accesses to the memory. As the number of accesses to the memory at any given time can only be limited (e.g., one for a single ported memory), some memory access requests may be blocked while others are being processed.
Such blocking may be undesirable when network application data (or pixel data elements thereof) are being retrieved, for example, when the network application data is sought to be retrieved for refreshing a display screen of a television system. If the requests to retrieve network application data from the memory are not serviced (processed) in a timely fashion, network application data may not be available when required for generating display signals. As a result, display artifacts may result in the display on the displays screen. Such display artifacts may be undesirable.
Therefore, what is needed is a method and apparatus which enable the network application data to be retrieved from a memory in a timely fashion in the face of other types of accesses to the memory.